Influence of Octadecyltrichlorosilane Surface Modification on Electrical Properties of Polymer Thin-Film Transistors Studied by Capacitance–Voltage Analysis

The influence of octadecyltrichlorosilane (OTS) surface modification of a gate dielectric on the electrical properties of polymer thin-film transistors based on poly(3-hexylthiophene) is investigated by using capacitance-voltage analysis. Results show that surface modification using OTS can effectively increase the field-effect mobility in the saturation region by almost two orders of magnitude to 2 × 10² cm²/V · s and improve the stability of the devices under gate-bias stress. Capacitance-voltage (C-V) analysis for the metal-polymer-oxide-silicon structures indicates that the frequency-dependent behavior of the C-V characteristics is related to the long relaxation time of the charge carriers in the polymer bulk rather than the trapping effect at the dielectric/ polymer interface, and the performance improvement of the de vices is attributed to a reduction of localized charges in the poly mer bulk.